This invention relates to cooperative drive robots.
A conventional robot for moving a heavy load such as an article, a tool, or a cargo to a desired position is as shown in FIG. 1, for instance. That is, a swingably driven driving box 3 is mounted on the upper portion of a base in the form of a pole 2 erected on a truck 1, and horizontal arms 4 form a parallelogram link mechanism which is coupled through a balancing spring 5 to the box 3. A vertical arm 6 is extended downwardly from one end of the horizontal arm 4, and a holding section 8 for holding a load 7 is provided at the lower end of the vertical arm 6. The load can be held by closing a holding member 9 provided on the bottom of the holding section 8. The circular movement of the robot, the vertical and horizontal movements and circular movement of the holding section 8, and the opening and closing operations of the holding member 9 are controlled by a control box 10. This control box is employed to move the holding section 8 vertically and/or horizontally to carry the load to a specified position in accordance with position data from a preset program or a computer. However, the weight of the load 7 is not always constant, and therefore the arms 4 and 6 may be somewhat bent because of variations in weight and moving speed. Therefore, even if the holding section 8 is moved in accordance with the position data specified, the actual position of the load 7 carried by the holding section 8 is different from the specified position.
The circular motion of the driving box 3 is one of the factors which will lower the positional accuracy because there is a space between the driving section and the holding section. In other words, in carrying a load by holding it with the arm of the conventional robot, the arm is turned by applying a driving force to the base of the arm. Accordingly, it is difficult to accurately carry the load to the specified position because of the bending, the inertia, and the circular motion of the arm.
Furthermore, where there is a distance between the holding section and the driving section at the base of the arm in the conventional robot, it is necessary to increase the structural strength of the arm and also the driving power, and this leads to an increase of the inertia and the size of the robot. This is another disadvantage of the conventional robot.
In addition, in the case where it is required to lift and carry a load and to place it at a specified position with high accuracy, heretofore one robot is used, and a position instruction obtained through an intricate correction calculation in a computer or the like is issued to the robot. Accordingly, the robot control system is necessarily intricate and expensive.
Moreover, depending on the position of the load 7, it is required to control the holding direction of the holding section 8 which is the hand of the robot. If it is necessary to maintain unchanged the holding direction of the holding section, the direction control must be carried out by intricate calculation. This is an additional drawback accompanying the conventional robot.